Abstract
Parasitic organisms in cells are activated by damages in the host cells. In mammalian genomes, there are large numbers of retrotransposons that resemble to genomes of retrovirus. Although we found cDNA of retrotransposon, intracisternal A-particle (IAP), is frequently inserted into genomic DNA of radiation-induced myeloid leukemia cells in C3H/He mouse, the molecular process of IAP-mediated retrotransposition following to radiation in mouse cells has not yet been clarified. We studied radiation effect on IAP cDNA synthesis in RAW264.7 based on our original method to measure reverse transcript from expression vector by real-time PCR.
As reporter genes to measure reverse transcription, both entire and deletion types of IAP DNA element that possess unique nucleotides were constructed and stably introduced in RAW264.7 mouse macrophage cells. Transforming cell lines that continuously expressed IAP RNA were x-irradiated and the levels of RNA and cDNA from the transgene were quantified. We found that the level of cDNA from transgene IAP RNA increased 24 hours after radiation in the doses from 2 to 5 Gy, even though the RNA level was kept at a constant level. This suggests that reverse transcription is activated by radiation damage in mouse cells and that radiation stimulates obscure cellular mechanism including retroviral reverse transcription .
